1. Field of the Invention
The present invention relates to integrated circuits and, more particularly, to techniques for mounting integrated circuits onto printed circuit boards.
2. Description of the Related Art
As integrated circuits become more complex, gate density, number of gates and fabrication complexity of integrated circuit chips all tend to increase. The power consumed by these integrated circuit chips has similarly increased as the number of gates has increased. Due to the increases in gate densities, number of gates and power consumption within many integrated circuits chips, it becomes important to manage the heat generated by these integrated circuit chips to prevent overheating. Specifically, it becomes necessary to provide a cooling device (e.g., a heat sink) to cool many integrated circuit chips. For example, high performance integrated circuit chips such as high performance microprocessors typically must be cooled. Typically, the cooling device is a heat sink which is placed on the integrated circuit chip to be cooled. The heat sink has high thermal conductivity so that heat is dissipated along its surface area which is substantially larger than the surface area of the integrated circuit chip to be cooled. The heat which is transferred to the heat sink from the integrated circuit chip is then dispersed into air which surrounds or flows over the heat sink. The air flow is typically provided by a fan. Complicated liquid cooled heat sinks have also been used for more demanding cooling tasks.
FIG. 1 is a diagram illustrating an example of a mounting 100 of an integrated circuit chip to a printed circuit board using conventional techniques. Specifically, FIG. 1 illustrates a printed circuit board 102 having integrated circuit chips 104 and 106 mounted thereon. The integrated circuit chips 104 and 106 in this illustrated embodiment are mounted directly to the printed circuit board 102 using pins 108. The pins 108 could, for example, be pins of a Pin Grid Array (PGA). Alternatively, a Ball Grid Array (BGA) mounting technique could use solder balls instead of the pins 108. Also, assuming that the integrated circuit chip 104 is a high performance device which requires a heat sink, a heat sink 110 is placed on the top of the integrated circuit chip 104. The heat sink 108 is typically held in place using an adhesive 112. The adhesive 112 preferably has a high thermal conductivity. The heat sink 110 could also be held in place with screws, bolts or clips.
A problem with the mounting 100 approach as illustrated in FIG. 1 is that when the printed circuit board 102 or the system (e.g., cabinet, box, machine, etc.) in which the printed circuit board 102 resides is subjected to impulse forces or vibrations, the mass of the heat sink 110 together with the mass of the integrated circuit chip 104 induce an inertial load on the pins 108. An impulse force could arise from a number of situations any of which tend to accelerate the printed circuit board 102 or the system in which the main printed circuit board resides. For example, the printed circuit board 102 or the system may be accidentally dropped onto the floor, a shipper may throw or jar a box containing the printed circuit board 102 or the system a substantial distance, and the like. The resulting inertial load on the pins 108 can be substantial, particularly when the mass of the heat sink 108 is substantial. As a result, the pins 108 of the integrated circuit chip 104 are subjected to loads (inertial loads) which are substantially larger than they are design to withstand. Consequently, impulse forces or vibrations can cause the pins 108 (or other mounting technique) to break or otherwise become damaged such that the integrated circuit chip 104 is no longer reliably electrically connected to the printed circuit board 102.
Thus, there is a need for an improved technique for mounting an integrated circuit chip to a printed circuit board such that inertial loads, particularly those associated with the mass of the heat sink, are shielded from damaging the connections between the integrated circuit chip and the associated printed circuit board.